In a typical multi-function document reproduction system, a photoconductive drum or photoreceptor belt rotates at an angular velocity and, as the photoconductive drum rotates, the drum is electrostatically charged. A latent image is exposed line-by-line onto the photoconductive drum using a scanning laser and, for instance, a rotating polygon mirror. The latent image is developed by electrostatically adhering toner particles to the photoconductive drum. The developed image is transferred from the photoconductive drum to the output media such as paper. The toner image on the paper is fused to the paper to make the image on the paper permanent. The surface of the photoconductive drum is cleaned to remove any residual toner on the surface of the photoconductive drum. Typically, the printing device drives the photoconductive drum using a motor drive system or a motor drive train. The motor drive system has a substantial amount of external loading because it typically drives the auxiliary rollers and transports the paper through a series of gear trains. With the additional external loading, as well as periodic disturbances due to imperfections in the series of gear trains, the motor drive system imparts a varying velocity on the photoconductive drum. The varying photoconductive drum velocity causes scanline spacing variation in the printed image. The scanline spacing variation is a significant contributor of artifacts in the marking process. For example, halftone banding caused by scanline spacing variation is one of the most visible and undesirable artifacts, appearing as light and dark streaks across a printed page perpendicular to the process direction. Such one dimensional image density variation in the process direction are often periodic and can result from errors in the mechanical motion of rotating components within a marking engine. These components may be gears, pinions, and rollers in the charging and development subsystems, photoreceptors and their drive trains, or the ROS polygon.
Many Xerox production color systems (iGen3 and iGen4, DC8002, DC7002) now include an In-Line-Spectrophotometer (ILS). Systems such as the DC8002/7002 are susceptible to a banding defect. Current ILS implementations do not include mechanisms to robustly deal with banding. The control loop for color management uses the ILS for measurement of the current system state. If a patch falls within an area with banding on a print, the system will read and calibrate according to the readings for that patch. Both dot linearization and characterization (ICC profile generation) use the ILS patch reads to generate new dots and profiles in-situ. The accuracy of the profiles and channel-by-channel correction are limited by the accuracy of the patch measurements. The accuracy of these measurements is dependent on several factors including: ILS repeatability, ILS accuracy, and xerographic variation. ILS repeatability has been shown to be very low and ILS accuracy has been addressed previously via the Spectral Component Analysis (SCA) matrix.
Accordingly, what is needed in this art are increasingly sophisticated systems and methods for creating a dynamic document comprising constant color patch targets whose distance between patch repeats is optimal for reducing banding noise in ILS measurements.